* Astronomy

Blobrana · L

RE: Sloan Digital Sky Survey

Blobrana · L

Title: A Catalogue of Bulge+Disk Decompositions and Updated Photometry for 1.12 Million Galaxies in the Sloan Digital Sky Survey
Authors: Luc Simard, J. Trevor Mendel, David R. Patton, Sara L. Ellison, Alan W. McConnachie

We perform two-dimensional, Point-Spread-Function-convolved, bulge+disk decompositions in the g and r bandpasses on a sample of 1,123,718 galaxies from the Legacy area of the Sloan Digital Sky Survey Data Release Seven. Four different decomposition procedures are investigated which make improvements to sky background determinations and object deblending over the standard SDSS procedures that lead to more robust structural parameters and integrated galaxy magnitudes and colours, especially in crowded environments. We use a set of science-based quality assurance metrics namely the disk luminosity-size relation, the galaxy colour-magnitude diagram and the galaxy central (fibre) colours to show the robustness of our structural parameters. The best procedure utilises simultaneous, two-bandpass decompositions. Bulge and disk photometric errors remain below 0.1 mag down to bulge and disk magnitudes of g \simeq 19 and r \simeq 18.5. We also use and compare three different galaxy fitting models: a pure Sersic model, a n_b=4 bulge + disk model and a Sersic (free n_b) bulge + disk model. The most appropriate model for a given galaxy is determined by the F-test probability. All three catalogues of measured structural parameters, rest-frame magnitudes and colours are publicly released here. These catalogues should provide an extensive comparison set for a wide range of observational and theoretical studies of galaxies.

Read more (1874kb, PDF)

Blobrana · L

Title: The Seventh Data Release of the Sloan Digital Sky Survey
Authors: K. Abazajian, et al, for the Sloan Digital Sky Survey

This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most of the roughly 2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalogue contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry over 250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A coaddition of these data goes roughly two magnitudes fainter than the main survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2 in the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalogue (UCAC-2), reducing the rms statistical errors at the bright end to 45 milli-arcseconds per coordinate. A systematic error in bright galaxy photometry is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat-fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.

Read more (841kb, PDF)

Blobrana · L

This summer, after eight years of charting the cosmos, Dan Long and his colleagues completed the deepest, most comprehensive map of the heavens ever produced.
Known as the Sloan Digital Sky Survey, it is a three-dimensional model of the universe that allows an observer to travel, as if by rocket ship, from the dwarf galaxies hugging the skirts of the Milky Way to the most distant quasars, billions of light-years away.

Read more

Blobrana · L

The Sloan Digital Sky Survey's 3-D guide to the final frontier

Read more

Blobrana · L

Astronomers join new phase of Sloan Digital Sky Survey
Astronomers at Case Western Reserve University are participating in the newest phase of the Sloan Digital Sky Survey (SDSS), the most ambitious survey of the sky ever undertaken.
Located in Apache Point, N.M., the SDSS began mapping the night sky in 2000. The third phase of SDSS began in July 2008 and Case Western Reserve is an active collaborator throughout its six-year agenda, said Heather Morrison, professor and chair of the department of astronomy at the university.

Read more

Blobrana · L

After a decade of construction and eight years of operation (SDSS-I, 2000-2005; SDSS-II, 2005-2008), the Sloan Digital Sky Survey (SDSS) completed its observations in mid-July and will release its final data set to the public in October. SDSS-III, a six-year program composed of four new surveys, has now begun, using the same telescope.

Read more

Blobrana · L

The Sloan Digital Sky Survey (SDSS) is the most ambitious astronomical survey ever undertaken. When completed, it will provide detailed optical images covering more than a quarter of the sky, and a 3-dimensional map of about a million galaxies and quasars. As the survey progresses, the data are released to the scientific community and the general public in annual increments.

Read more